Electric furnace



G. M. LITTLE ELECTRIC FURNACE April 14,1925. 1,533,255

Filed Nov. 1, 1922 WITNESSES: INVENTOR Geofise M. Little.

so 7 V of the furnace} w Patented Apr. 14, 1925. I

UNITED STATES 1,533,255 PATENT OFFICE.

GE EGE M. LITTLE, 0F PITTSBU R-GH, PENNSYLVANIA, AssIGNoE ro wEs'nNeHoUsE ELE'cTEIc- & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC FURNACE.

Application filed November 1, 1922. Serial No. 598,318.

To all whom it may concern:

Be it known that I, GEORGE M. LI'rrLE, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric Furnaces, of which-the following is a speci fication.

My invention relates to electric furnaces, and particularly to electric-resistance furnaces.

The object of my invention is to provide a relatively simple, rugged, built-up carbonaceous resistor having arelatively high electricresistivity: 7 i 7 In practicing my invention, I provide a plurality of relatively thin, flat, carbonaceous plates spaced apartby current-conducting refractory members of relatively small area placed therebetween adjacent-one edge thereof, and means for maintaining said spacing members in their proper operative positions.

f. I provide also auxiliary spacing members of relativelyhigh electric resistance located between'said plates adjacent another-edge thereof. Resilient compressing means is provided tomainta'in the flat plates and the spacing members in'close operative engagement Witheach other during the'operation In thesingle sheet of drawingsyf; Figure'l is a view, in vertical longitudi} nal section, of an-electric-resistance:furnace comprising the device embodying my in- VBl'ltlOIl," i T 3 Yr Fig. 2 isa vievv, invertical lateral section, taken on the; line IIII of Fig. 1,

Fig. 3 is a view', in side elevation, of a modified form of resistor embodying my invention, I

Fig. 4 is a view,- in side elevation, of another modification of resistor embodying my invention, i Fig. 5 is a view, in side elevation, of a further modification of a resistor embodying my invention, and f F ig. 6 is a view, in end elevation, of the resistor illustrated in Fig. 5.

An electric furnace, designated generally by the numeral 11, comprises an outer metallic casing 12 which is provided with a plurality of supporting members 13 suitably secured thereto. An outer lining 14: comprises a plurality of bricks or blocks of any suitable refractory heat-insulating material, usually employed in the art. An inner lining 15- comprises a plurality of bricksor blocks of. a. suitable refractory high-temperature-resisting.material. The bricks or blocksconstituting the. two linings 14 and 15 are so spaced and'locate'd as to provide a' chamber, which is divided into a workreceiving. chamber 16 and a heating c' hambei 17, which chambers may located in any'suitableror desired relation relatively to each other but' are hereshoWnaSilocatedin superposed position. .A. suitable refractory high-temperature resisting fplate .',18' is employed to separate the. tWQjQhambers 16 and 17 from each other. .A s'uitableope'ning 19 P e n' o ofith'eivallspithe furnace to-permit of introducing material tribe heatetreated into the chamber 16;and of rem ving it thcrefro 5 1.; ...-i A heating element,'jvhich' 1n ay;be designatedagenerally by the; numeral;-.2 com prises fa plural ty of relativel -thi ,flat re fractoryPliltfiSQZ which may consist ofcan. boazor g aphi or, any. s mi ar re istame materiah SID:- i e; t q mlp heat na elem n illustrated' more particularly ifi Figali of the drawings, the? fiat 5 plates (22 are,g1nai nmined paced-apa re at e a ztb ni Peirends y refle ors re st r-mem e s2 h hia z fsu !anti l xihshapa l t section. The joverhanging portion of; the members of 'E-shape insure-that?they .-yvi1lbe supported" in isubstantiallygthe positions illustrated in Fig. l ofvthe dravving during the operation of ,the furnace; ,';l h e areaof cross-section traversed by an'electric; current ismade relatively small by suitably; reduc; ing the height of the members ;23. {,Any,de; sired number of flat plates'i22'and'of -the members 23,:of ;T.-sh'ape, .may be employed, oras maybe permitted by ithej longitudinal dimensions .of they furnace chamber. {17, I r Asuitable refractory .conductingblock 24 is located in operative engagement with the outer flat plate 22 :at 'eacht'en'd of the heating element, and iis,-.in turn, operatively engaged by theinnene'ndiof: an elongated refractory: carbonaeeousi electrode 25. The

outer taperingend of each'of the electrodes 25 fits into a suitably shaped opening in'a Water-cooled electric-circuit-terminalv member 26. An annular member 27, made of a suitable high-temperature-resisting electricinsulating material, such as certain forms of asbestos, is loated immediately adj acent the outer surface of the furnace wall and surrounding. the water-cooled terminal member 26"infordi: maintain itfin its proper operative position and to"prevent leakage of current therefrom into the metalcasing 12.

Means for maintaining the .plates122 and the current-conducting and spacing members 23in close operative engagement comprises a helical spring' 28, the outer. end of which engages a fixed-member 29 which, as illustrated in Fig.- 1, comprises av relatively heavy bent metal member, one end of which is secured to the metalcasing 12. A rod 31, the inner end of which is threaded and is provided with an adjusting nut- 32 and a washer 33, extends through the helical spring 28. The inner end of the rod 31 engages-the outer surface of an insulating plate 34 which'is located against the outer surface of the water-cooled terminal block 26. Any desired amount of pressuremay be obtained by sui tably adjusting the nut 32 on thethi'eaded-iod 31. 1

element 21 an lural ity o'f relatively" small; refractory=blocs 35'a're placed between each adjacent pair of plates 22 nearithe-lower edgeth'ereo'f: The 1 thiclmess' of; the blocks '-is s ibstantiallyi' equal to thatoi the current-conductingspacing" members :23 lo.

cated at the top ofthe at plates 22, Any

' dearer material maybefemployed in" mak that the {em-"rent tfaversing 1 fizsiinaedesira ie a' these; spaci g members f 35; -suchas an lecti'ie iiisiilating frefractorf-materialfor a material s 'eh as' 'ch'a coal; vvhich' is of relativelyfhigh "electric resi' stancef-g If it is ni ame-sage os tiie raresi2a the area'of uiese 'ismaae very sma ran-d ds fewspacing blocks pbssjblef are leiflplpyed inorder these block s 'shalP'be relatively' 'vei y*smalls i; its-illustrat d more particularly. :in Figs. ran-a 2 0T: the drawing, the plates 22 may O'f'sirchj "ii'nen'sion that their 'Ll ovver-i edges i 'est upon tlie floon of the heating: chamber ;17 in "which 'case, -itf :is' necessary :.-that the refractorymaterial employed forthe inner lining- 15' shall: be non-conducting even at the l relative high temperatures eirperien'ced 'duringtl're operationof such: a furnace; I By employing: :a :-.-refractory diaphragm -18- and placing it between the work-receiving openi-ng- 19 and? the carbonaceous" heating element-' 21", the' -Iatter is protected againstl the oziidiz'ing effect of. air engaging the opening 19'during the operation of the furnace. The distance between the top part of' the heating element 21 and the, dia- -phragm '18 is madeverysmall in order that the-distance through which the heat from .the heating element 21 must flow to reach stabilize the bunt-li hating.

the work-receiving chainber 16 shall be as small as possible.

The relative locations of the heating chamber 17 and of the work-receiving -inbefore; described shall be so located between the adjacent flat plates 22 that the current path provided thereby is immediately adjacent the diaphragm 1S separating the two chambers from each other.

A modified form of heating element is illustrated in Fig. 3 of the drawing, in which the current-conducting spacing members. comprise rectangular narrow fiat bars 36 located adjacent one edge of the plates Thin flat-supporting members 37 are placed between the spaced plates 22 and are of such dimensions that they will extend from substantially the lJOttO-lll ot the ba1's 36 to the bottom of the plates In constructing such a furnace, I have found it possible to use a piece of wood of suitable dimensions for the supporting member 37 which: was changed into charcoal upon the initiaLheating-up: of the furnace and which operated ve'ry satisfactorily as a supporting means for the bars 36.

" Referring to Fig. 4 of the drawings, the plates 22 may be spaced apart at their upper edges by a relatively narrow mass 38 of granular current-conducting material, such as finely divided carbon or coke, and supporting. members 37, as hereinbefore described in 'cor'mection with the illustration described in Fig; 3, maybe employed.

plurality of small flat plates 39 may fifbe'em'ployed ascurrent-conducting members and: 6 0f the drawings..- By'tliis i members ofrefractory' material and of much smaller area of cross-section. The current- 1 conducting spacing members may be located -at;any suitable or desired position on the plates to insure that the'heat generated by a'current traversing the path is generated adjacent a Work-receiving chamber or ad- 1 .Ja'cent a-locatron m winch the material to .he heat-treated is placed.

This application is closely related to my .co-pendin'g application,- Serial No. dii-lfl'TG,

filed March 23, 1921.

Various modifications and changes in detail and general arrangement may be made Without departing from the spirit and scope of the invention and such modifications are intended to be covered by the appended claims.

I claim as my invention:

1. An electric furnace resistor comprising a plurality of relatively thin, flat, refractory plates, a plurality of current-conducting spacing members of relatively small area alternating with said fiat plates, and means for maintaining said spacing members in proper operative positions relatively to said fiat plates.

2. An electric furnace resistor comprising a plurality of relatively thin, flat, refractory plates, a plurality of current-conducting spacing members of relatively small area alternating with said flat plates and located adjacent the top portion thereof.

3. In an electric furnace, in combination, a heating element comprising a plurality of relatively thin, flat carbonaceous plates, having their flat surfaces located in spacedapart relation relatively to each other, a plurality of current-conducting spacing members, of relatively small area, alternating with said fiat plates, means for supporting said spacing members, and resilient compressing means for said plurality of plates and spacing members.

4. In an electric furnace, in combination, a plurality of refractory walls enclosing a furnace chamber, a carbonaceous diaphragm dividing said chamber into a heating chamher and a work-receiving chamber, a heating element in said heating chamber comprising a plurality of relatively thin fiat, carbonaceous plates, a plurality of current-com ducting spacing members, of relatively small area, alternating with said fiat plates and means for maintaining said spacing members in proper operative positions relatively to said flat plates, and resilient compressing means for ensuring close operative engagement between said flat plates and said spa:- ing members.

5. An electric furnace resistor comprising a plurality of relatively thin, flat, carbonaceous plates, a plurality of currentconducting spacing members of relatively small area alternating with said flat plates and located therebetween adjacent one edge thereof, and auxiliary spacing members of relatively high electrical resistance located between adjacent fiat plates near another edge thereof.

6. An electric furnace resistor comprising a plurality of relatively thin, fiat, carbonaceous plates, a plurality of current-conducting spacing members of relatively small area alternating with said flat plates and located therebetween adjacent one edge thereof, auxiliary spacing members of relatively high electrical resistance located be tween adjacent flat plates near another edge thereof, and resilient compressing means for maintaining said fiat plates and said spacing means in close operative engagement with each other.

In testimony whereof, I have hereunto subscribed my name this 27th day of October 1922.

GEORGE M. LITTLE. 

